Selector mechanism



NOV. 16, 1948. 1 HE'RR SELECTOR MECHANI SM 4 Sheets Sheet 1 Original Filed Sept. 17, 1947 mZOrrdFmmDm i N \l INVENTOR.

Nov. 16, 1948. D. L. HERR 2,453,911

SELECTOR MECHANISM Original Filed Sept. 1'7, 1947 4 Sh ets-Sheet 3 INVENTOR. flmzald L H011; BY ,1

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Nov. 16, 1948. HERR SELECTOR MECHANISM Original Filed Sept.

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flTTOM Nov.'16, 1948. o. L. HERR SELECTOR MECHANISM 4 Sheets-Sheet 4 Original Filed Sept. 1'7, 1947 6/ .I IupIIIIIIIIIIIHH INVENTOR. flonald L. Herr,

Patented Nov. 16, 1948 SELECTOR MECHANISM Donald L. Herr, Milwaukee, Wis, assignor to Control Instrument Company, Inc., Brooklyn, N. Y., a corporation of New York Original application September 17, 1947, Serial No. 774,613. Divided and this application May 25, 1948, Serial No. 28,975

This invention relates to improvements in selector mechanisms adapted for automatically controlling the selective interconnection between various instrumentalities, the present application being a division of my co-pending application Serial No. 774,613, filed September 17, 1947.

It has been the practice in different types of switching systems to use a multiplicity of instruments, some of which may be controlled by the operation of others, and to provide for manually establishing interconnection therebetween so that one or more of them may be operatively connected to any or all of the others.

The present invention proposes an improved means wherein such diversified interconnection is accomplished by the arbitrary selection of any one of a plurality of control elements, each having diiierent media thereon for identifying one of a plurality of modes of connection, and by causing the selected element to automatically establish or control the establishment of the desired connection.

The invention further proposes an improved mechanism wherein the selection of any one of the plurality of grouped control elements is effected rapidly and accurately.

The inventive idea involved is capable of receiving a variety of expressions, one of which, for the purpose of illustration, is shown in the accompanying drawings; but it is to be expressly understood that said drawings are employed merely to facilitate the description of the invention as a whole and not to define the elements thereof, reference being had to the appended claims for this purpose.

In the drawings:

Fig. 1 is a diagrammatic View showing the circuits employed in controllin the operation of the selector mechanism;

Fig. 1a is a diagrammatic View of a remote selecting device employed to transmit signals to the selector mechanism;

Fig. 2 is a top plan view of the selector mechanism;

Fig. 3 is a fragmentary end elevation of said mechanism showing the parts at an intermediate stage of the operation thereof Fig. 4 is a transverse section on the line l l of Fig. 2 with parts in the position shown in Fig. 3;

Fig. 5 is an enlarged fragmentary sectional View, somewhat similar to Fig. 4, illustratin the mechanism in position after a selecting operation has been completed;

Fig. 6 is a section on the line 6-5 of Fig. 2;

Fig. 7 is a section on the line 'l'l of Fig. 2;

Fig. 8 is an elevation, partly in section, showing a portion of the drive mechanism for the selector;

Fig. 9 is a side elevation, partly in section, of

8 Claims. (Cl. 177-353) the selector mechanism showing the banks of switch contacts and the means for controlling the same.

The invention herein shown may be employed in conjunction with various type ofswitching systems such as used for gunnery fire control or electric power distribution wherein interconnections are to be established between a multiplicity of instruments.

In conformity with the present invention it is proposed to establish interconnections between various instruments by controlling, from a-point or points remote from the selector mechanism, the automatic selection, from a plurality of control elements, that one which has thereon the identifying media individual to the desired interconnection and to utilize the selection of the said control element to establish the connections identified thereby. The number of control elements, and the possible number of interconnections is wholely arbitrary and depends entirely upon the requirements of the system to which the invention is to be adapted. These elements are located in the selector mechanism which operates to select the control element required to establish any desired connection.

In some systems it may be desirable to efiect the selection of a control element within the selector mechanism from any one of a plurality of remotely connected substations 251, 252, etc., through a station selector switch 26 which may be manually controlled and be located wherever the selector. mechanism is employed. The embodiment herein shown utilizes and illustrates this remote selection; however, the control element selecting switch 28 (Fig. 1a) hereinafter described may, of course, be an integral part of the selector mechanism so that selection of the control elements is available immediately at the mechanism itself, and not necessarily from a remote station.

For the remote selection of the control elements, said control element selector 28 having a plug 29 is adapted to be connected to an output at any one of the remote selection points 251, etc., and, by telephonic or other means (not shown) information may be obtained from an attendant at the selector mechanism identifying the particular control element then in effect. Should a change in the set-up efiected by the selector mechanism be desired, the attendant will cause the remote station selector switch 26 to be operated so as to connect any one of the remote selection points 251, 252, etc. with the selector mechanism. The operator at the designated remote selection point ma then press a key (see Fig. la) individual to the desired control element within the selector mechanism required to establish the desired connections, and this action will produce a signaling impulse through the plug 29 now connected to the remote selection point, which will initiate the operation of the selector mechanism.

The selector mechanism proper comprises a supporting base 30 upon which are mounted two banks of switches generally indicated at 3| and 32. Each bank comprises any number of normally open switch contacts 33 and 34 which may be required and which contacts may be closed to effect the particular switching operation required, either to establish a circuit (not shown) directly by way of switches 3|, 32 and their contacts 33 and 34, or by way of relays as shown in said copending application. Two perpendicular frames 35 are secured to the base 3|! adjacent the ends of said b'anlis or switch-es and have mounted thereon a stationary guide plate 36 which supports a horizontal frame 31. Outwardly of the end frames 35, the base 30 also supports two pairs of standards 38 utilized to guide a vertically movable press numher or plate 39 which, as will presently appear, controls the closing of selected sets of contacts in the banks 31, 32 in its downward movement and which is raised during an interval of the operation of the selector mechanism when any one of a plurality of stacked control elements 40 is being selected, there being six of such elements shown herein, one for an ofi position in which all of the contacts 33 and 34 are open, and the remaining five for operatin the switches 3|, 32 and closing various combinations of contacts 33 and 34 as may be required. Each element is in the form of a rectangular plate and is provided thereunder with a supporting holder 4| which is adapted to be reciprocated in a transverse direction to adjust its plate 40 from inoperative to operative position when it is selected for the control of switches 3|, 32 individual thereto. In order that each plate will be shifted with its holder. the former is provided at each end with a longitudinal slot 42 (see Figs. 2 and 7) which receives a stud 43 carried by the holder. Said holders have struck therefrom along adjacent longitudinal edges the angular flanges 44 '(Fig. 6) all of different lengths and, when the holders are stacked, the flanges of increasing length toward the top of the stack will project downwardly through the lower holders and will be longitudinally spaced for connection to a mechanism later to be described which will successively reciprocate the holders during the selection of one of the elements 40. To support the elements '40 and their holders in stacked position and for individual selection, the same are placed upon a base plate 45 mounted on the frame 31 above the plate 36 and, in order to prevent endwise shifting or the elements 40, 4|, vertical guide rollers 46 '(Fig. 9) are carried by the frame 31 at each end thereof for contact with the end or transverse edges of said elements. After being so stacked, a removable weighted member 41, having end flanges 48 which engage with the ends of the frame 31, is placed in position over the stack and said member and flanges are provided with rollers '49 which then engage the top element 40 at its center and ends, whereby the stacked elements will be maintained in their respective horizontal planes at all times during the operation of the selector mechanism. By means of such construction, it will be apparent that the holders and their plates may be removed and other plates substituted whenever it is desired to obtain contact combinations other than those capable of being established by the removed Plates.

Each element or plate 40 is individual to one combination or contact selection and has means aligned with said slots 50, 51 so that when all the plates and holders are stacked the slots therein are in vertical alignment. The slots 50, 5| or" each plate are arranged in two rows, as shown in the top plate of Fig. 2, and the number of slots is equal to the number of switch contacts in the banks 3|, 32 which are, in turn, equal to the number of circuits the instrument can independently control. Also, there is provided a switch operating or transfer device, generally indicated at 53, for each group of vertically align-ed slots in the various plates and their holders, and said device is individual to one of the switch contacts in the banks 31 or 32, and is designed to close said contacts after the device is adjusted to its operative position by the presence of short slots 5| in a plate 40 when the latter is shifted by its holder 4|. Each device 53 comprises the upper and lower pin sections 54 and 55 the former of which extends upwardly through the plates and 45 and the assoelated vertically aligned slots 50, 5| and 52 in the elements and their holders 4|. The sections 54, 55 are pivotally and slid-ably interconnected by a vertical slot 56 in the lower end of the section 54 which receives a pin 57 on the upper end of the section 55. The sections 54 of the various devices 53 are supported for sliding movement by flanges 58 engaging the plates 36 and and, by reason of the transverse slots 59 in said plate 36, are capable of sliding movement to the right, as viewed in Fig. 5, against the tension of the return springs 60 when the upper ends of the sections 54 are engaged by the ends of short slots 5| appearing in a plate 40 which is being selected by a shifting of its holder 4| to the right. However, where lon slots appear in the selected plate 40, the shifting movement of the latter will be relative to the pin sections 54 which extend through said lon slots, and no sliding movement of the latter Jpin sections will result. The lower section of each device 53 is pivoted intermediate its ends to the press member 39, and when in its normal tilted position and with the press member lowered, the lower end of said section is disposed alongside its associated switch contact in the banks 3|, 32 as shown at the left of Fig. 5.

The selection of a control member 40 is accomplished after the press member 39 has been elevated to the position of Fig. 4, and this elevation raises the pin sections 55 relative to their sections 54 by reason of the slot and pin connections 56, 51 therebetween, thus elevating the lower ends of the sections 55 to points above their associated switches 3|, 32. After the member 39 and sections 55 are thus raised and a control plate 40,

for example the top one in Fig. 5, is selected by shifting the same and its holder 4| to the right as shown, wherever a short slot 5| appears in said plate with its left end engaged with the upper end of the pin section :54 projecting through said slot, the shifting of said plate will slide said section 54 to the right in its slot '59 thus causing the associated pin section '55 to be rocked about its pivot to a vertically aligned position with respect to its section 54 and directly over the set of switch contacts individual to the device 53' thus operated. The extent of shifting movement of the plate 40 and its holder 4| to the right is not sufiicient to cause the long slots 50 in said plate to slide the upper pin sections 54 which extend therethrough, as will be seen at the left of Fig. 5. When the devices 53 have been thus operated, the press member 39 moves downwardly to carry with it all of the lower pin sections 55, and those which have been vertically aligned with their sections 54 are caused, by said downward movement, to engage with the upper contacts of the switch contacts in the switch banks 3|, 32 so that said contacts will be closed when the press member has reached its lowermost position. number of short slots appearing in the selected control plate 43 and their placement therein, a like number of switch contacts will be closed to complete the circuits to which they may be individual and which circuits are identified by the position of the short slots 5| in said control plate.

The sequence of operation of the selector mechanism is such that the press member 39 remains in its down position as long as a selection of a control member 4|.) is maintained. When another selection is initiated, the press member will begin its upward movement under the control of a press motor 6| to elevate the vertically aligned pin sections 55. Those which have been vertically aligned by a previous operation and engage with contacts 3|, 32 will, by reason of such elevation, permit such closed contacts to separate and thus open the circuits established thereby. When said press member has reached the extent of its upward movement, as in Figs. 3 and 4, a cam motor 62 is energized through a circuit established by the press motor, as will later appear, and said motor 62 then operates a series of cams 63 to 63, one for each control plate 40, to successively shift the holders 4| and their control plates 40 until the desired one has been selected whereupon the cam motor is stopped by the opening of its energizing circuit, with the selected control plate in its shifted position wherein it has operated to set one or more of the transfer devices 53 in their operative positions preparatory to closing the associated contacts 33, 34 in the banks of switches 3|, 32. As soon as the cam motor 62 stops, it reestablishes an energizing circuit for the press motor which now resumes its rotation from the point where it was stopped until it has operated to restore the press member 39 to its lower position. The selected switch contacts 33, 34 of switches 3|, 32 are now closed, and the corresponding circuits are established as identified by the selected control plate 40.

The operation and stopping of the press motor 5| is accomplished through a switch pile 69 in a manner to be later described in detail, and said motor is mounted on the base by a suitable support 10. A longitudinally extending shaft ll mounted in bearings 12 secured to the ends of said base 30 is driven by the shaft 13 of said motor 3| through worm gearing 14 and each end of said shaft 1 carries a gear 75 meshing with a similar gear 18 on a stub shaft 11 supported in the adjacent bearing l2. Each stub shaft 1'! carries a cam 18 (see Figs. 2 and 8) having an internal groove 13 for receiving a roller on one end of a lever 80 pivoted intermediate its end on the adjacent frame and having its other end connected to the press member 33 so that as the lever is rocked by an eccentric portion of the groove l9, said member 39 will be raised and lowered as previously described. In Fig. 3, the parts are Thus, depending upon the shown in the positions attained just prior to the press member 39 reaching its uppermost position in which the motor 3| will be stopped while-a selection is being made of a control plate 40. Upon movement of the cam 18 (Fig. 3) a slight distance farther, an external cam 8| thereon will operate the switch pile 69 to open the circuit for the motor 6| at the contacts 82, as will appear more in detail in the course of the description. The motor 6| then stops with said switch pile in reversed position and, after the proper control plate has been selected, said motor will again be energized to cause the cams 18 to rock the levers in a reverse direction so that the press member 39 will be restored to its lower position to accomplish the function of closing the proper contacts 33, 34 in the switch banks 3|, 32. As is well understood, clutch mechanisms (not shown) may be utilized to stop the cams 53 to 68 and T8 in proper positions upon deenergization of the respective motors 62 and 6|.

When, in the sequence above described, the press motor 3| is stopped and the cam motor 62 is energized, the latter will, through its shaft 83, drive the worm gearing 84 connected to the counter shaft 85 mounted in bearings 86 on the base 33; Operation of said shaft will rotate the var ious cams 83 to 58 thereon, and as said cams are turned they will, at certain points in their revolutions, operate the respective switch piles 81 to 32 for purposes which will later appear. Each of the cams 63 to 68 is provided with an internal groove 33 and the effective cam portions of all said grooves are radially offset relative to each other so that as the cams are rotated their respective grooves will successively control the rocking movements of associated bell cranks 94 pivoted on a standard on the base 33. The lower end of each bell crank has a roller engaging in the groove 93 of its cam, and its upper end is connected to the flange 4!; of one of the holders 4| so that as said cam is rotated its bell crank 94 will be rocked to reciprocate said holder and the associated control plate 43. The successive reciprocation of said holders continues until the one desired is in its operative or shifted position, as shown at the top of Fig. 5. Upon reaching such position, the associated cam, for example the cam 68, will operate its switch pile 92 to open the circuit for the cam motor 62 which will then stop with the selected holder and control plate in their right hand position wherein the transfer devices 53 actuated by the short slots 5| in said plate will then be in position to close their respective switch contacts when the press memher is lowered. Stopping of the cam motor 62 reenergizes the press motor 8| to lower the press member 39 as previously mentioned. It is to be noted that as control plates are successively reciprocated by their respective cams 63 to B8, certain transfer devices 53 will momentarily assume operative positions under the control of the short slots 5| in said plates, but as the unwanted plates are returned to normal by the complete reoiprocation of their holders, said operated devices 53 will also be restored by their springs 60 and thus the lower pin sections 55 of said devices will resume their tilted positions.

Referring to Fig. 1, it will be. seen that the switch wiper 95 of the substation selector 26 at the selector unit is in position wherein its movable contacts are in engagement with the vertical bank of terminals individual to the substation which is designated in Fig. l as 252; that the on key of the control element selector 28 (Fig.

1-3) is depressed and the corresponding switch pile 81 is operated. This condition caused by the depression of the "cfi key of said selector 28 resulted in the selection of the control element 40 which,'by its selection, effected the disconnection of all circuits by opening contact 33, 34:. Said condition continues until another element 49' is selc'otedby the depression of one of the keys A to E and said selection has resulted in the closure of the contacts in banks II 32 which are individual to the newly selected control element. The selector 28 is constructed in any well known manner so that only one key can be depressed at a time and the depression of any one of said keys will restore the previously operated key. Also, to avoid the possibility of the establishment of conflicting interconnections, any suitable time delay device I63 is included in the circuit of the selector 28 which will insure a sufl'icient lapse of time for the selector mechanism of Figs. 2 to 9 to operate before a new selection can be made. Six ofthe horizontal rows of terminals in the substation selector 26 are identified similarly to the keys of the selector 28 and are each individual to one of the control elements 40, and the other two horizontal rows of terminals in said selector 26 are joined to the line conductors LI and L2 connected to a suitable source of current (not shown) for operating the system.

It will now be assumed, for the purpose of i1- lustration, that it is desired to establish certain circuits by way of some of the switches 3.I and 32 to some switch operated devices (not shown) such as are disclosed in the copending application SrialNo. 774,613 of which this is a division, through the medium of a control plate 40 which is individual to the key A and to the row of terminals similarly designated on the selector switch 26, and that the signal or impulse for the establishment of such circuits is to be transmitted from the substation 251. It will be further assumed that the plug 29 has been inserted into the outlet at the aforesaid substation, that the selector switch 26 has been turned to the corresponding position and that the operator knows which control element is, at that moment, in service. By depressing the key marked A he may initiate the selection of one of the control plates 40, and by so doing any previously operated key on the selector will be restored.

Upon operation of the key A, a circuit is established for the press motor SI of the selector mechanism extending over the line conductor LI and through the motor, the now closed contacts 82., the conductor I common to the switch piles 81 and 92 associated with the cam motor 62, the closed contacts I96 of the switch pile 92, the conductor I and conductor I98 of the selector switch 25. The wiper I09 and terminal III] and thence through the plug and key contacts of the selector 28 connected to the substation 251, the conductor III leading from said substation, the terminal II2 of the selector 26, the wiper II3 engaged thereby, bus I I 4 and then over the line conductor L2 which is connected to said bus. The motor 6'I is thereby energized and in rotating the cams I8 in a counterclockwise direction, causes the press member 29 to be raised from its lowered position with the results previously described. As the cam 18 (Fig. 3) reaches the position shown its external cam BI engages with the arm of the switch pile 69 so that a small additional movement causes a reversal of the contacts of said pile thus opening the energizing circuit for said motor at the contacts 82 whereupon the motor comes to rest. Opening of the contacts 82 causes the closing of contacts H5 thereby energizing the circuit for the cam motor 62 extending over the line conductor LI, the conductor I I6 through the motor 62, the closed contacts H5, the conductor I and then over the previously described circuit through the closed contacts I06, the selector 26 and 28 and back to the line L2. The motor 62 now drives the shaft 85 to rotate the series of cams 6-3 to 68 thus successively reciprocating the holders 4| and their control plates 40 until the cam 68 individual to the desired control plate is actuated. This reverses the contacts of the switch pile 92 thereby breaking the energizing circuit for the cam motor at the contacts I06 causing the motor to stop with the selected control plate and its holder shifted to their operative position as shown in Fig. 5. During the rotation of the shaft 85 the cam 63 first permits the restoration of the switch pile 81 which was reversed by a previous operation, and the other cams 64 to 61 then momentarily and successively reverse their respective switch piles 88 through 9|. This latter action has no effect, however, since the terminals of the selector 26 joined to the latter switch piles are not connected by the substation now in use. 7

Reversal of the switch pile 92 establishes an energizing circuit for the press motor 6I which now extends over the line conductor LI and through the motorto the now closed contacts I I! of the switch pile 69, the conductor I I8, the closed contacts l IQ of the switch pile 92 and thence over the previously described circuit including the conductor I91 back to the line conductor L2. The motor 61 will then again operate until the cam ill on cam 18 (Fig. 3) disengages from the arm of the switch pile 69 to restore it and, in so operating, the cams l8 restore the press member 39 to its lowered position to close those switch contacts in the banks ill, 32 which have been selected by the short slots in the now selected control plate 40. Thereupon, said cams and motor SI come to rest. Restoration of the switch pile 69 closes the contacts I04 thereof to establish a signaling circuit to identify, at the selector mechanism, the particular control plate now in use which circuit extends over the line conductor LI through the contacts I-M, the conductor I20, the closed contacts I 2I on the switch pile 92, the lamp or other signal I22 and thence over the conductor I23 to the line conductor L2. This signal remains energized until the switch pile 92 is restored by a subsequent selection operation.

In this manner it is possible to select any or all of the switches 2|, -32 and operate them individually or simultaneously according to the combination indicated by the control plate making the selection to control a multiplicity of external circuits in a preconceived and prearranged manner. Since the switches 3I and 32 may be operated individually, simultaneously, or any possible group thereof at a time, a total of 24possible control plates exist, any five of which may be in use to perform the selection. .Any instrumentality whose function may be controlled by the opening or closing of a switch may be operated thereby and in the above identified parent application one such application to a fire control system is completely illustrated.

What is claimed is:

1. In a selector mechanism, a plurality of switch contacts to be operated, a group of selectable control elements stacked in a normally inoperative position and each individual to certain of sald'switch contacts, means to adjust one of said control elements in said stack to an operative position, a plurality of transfer elements normally having inoperative positions relative to said switch contacts and certain of which are movable to operative positions by the adjustment of said control element, and means operable subsequent to said adjustment to actuate the operated transfer elements to operate certain of said switch contacts.

2. In a selector mechanism, a plurality of switch contacts to be operated, a plurality of selectable control elements having media for identifying certain of said switch contacts, means to select one of said control elements, a plurality of transfer elements operable by said control elements and normally having inoperative positions relative to said switch contacts and certain of which identified by said selected control element are movable by its selection to operative position with respect to certain of said switch contacts, and means to thereupon actuate the operatively positioned transfer elements to operate the last named contacts.

3. In a selector mechanism, a plurality of switch contacts, a plurality of selectable control elements, means to select one of said control elements, a plurality of sectional transfer elements, certain sections of which are operated by the selection of said control element and the other sections of said transfer elements being responsive to the operation of the associated first named sections and having normally inoperative positions relative to said switch contacts and being adjustable to operative positions by the first named sections when said control element is selected, and means to then actuate said other sections to operate certain of said switch contacts.

4. In a selector mechanism, a plurality of switch contacts, a plurality of selectable control elements, means to select one of said control elements, a plurality of sectional transfer elements, certain sections of which are operated by the selection of said control element and the other sections of said transfer elements being responsive to the operation of the associated first named sections and having normally inoperative positions relative to said switch contacts and being adjustable to operative positions by said first named sections when said control element is selected, a press member to which said other sections are connected, and means to operate said press member to engage said other operated sections to operate certain of said switch contacts.

5. In a selector mechanism, a plurality of switch contacts to be operated, a plurality of selectable control elements having media for identifying certain of said switch contacts, a plurality of transfer elements each comprising sections having relative pivotal and linear movements, certain sections of all said transfer elements being operatively associated with the identifying media of said control elements, a press member to which the other sections of said transfer elements are pivoted, means to select one of said control elements to impart movement to certain of the first named sections of said transfer elements under the control of the identifying media on the selected control elements to thereby adjust the other sections of said transfer elements pivoted to said certain sections thereof and to said press member to operative positions relative to certain of said switch contacts, and means to operate said press member to move said adjusted other sections linearly relative to their 10 first named sections and into operative engagement with the last named switch contacts.

6. In a selector mechanism, a plurality of switch contacts to be operated, a plurality of selectable control elements having media for identifying certain of said switch contacts, a plurality of transfer elements each comprising sections having relative pivotal and linear movements, certain sections of all said elements being operatively associated with the identifying media of said control elements, a press member movable relative to said switch contacts and to which the other sections of said transfer elements are pivoted, means to move said press member in one direction relative to said contacts, means to thereupon select one of said control elements to impart relative, pivotal and linear movements between the sections of certain of said transfer elements individual to the identifying media on the selected control element to thereby operatively associate the latter transfer elements with certain of said switch contacts, and means operable at the conclusion of the selection of said control element for actuating the moving means of said press member to move the latter in a different direction to linearly adjust said other sections of the operated transfer elements into operative engagement with certain switch contacts.

'7. In a selector mechanism, a plurality of switch contacts to be operated, a press member movable relative to said contacts, actuating elements for said contacts carried by said press member in normally inoperative positions relative to said contacts, selectable control elements each having media for identifying certain of said switch contacts, means to select one of said control elements by moving the same to a position relative to the other control elements, and means coupled to said actuating elements to move certain of them identified by the media on the seelected control element into Operative position relative to the switch contacts also identified by the latter element, and means to then move said press member to operatively engage the last named actuating elements with the identified switch contacts.

8. In a selector mechanism, a plurality of switch contacts to be operated, stacked selectable control plates having long and short slots therein, the short slots identifying certain of said switch contacts, a holder for each control plate, individual operating means for each holder actuated by the selection of its plate to shift the latter to an operative position relative to the remainder of the stacked plates, transfer elements having portions extending through the slots in said plates with those extending through the short slots on a selected plate being thereby positioned, to the exclusion of the other transfer elements, into operative association with certain of said switch contacts, and means to operate said positioned transfer elements to operate the last named contacts.

DONALD L. HERR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,402,992 Elliott July 2, 1946 2,438,825 Roth Mar. 30. 1948 

